A drug formulary will be implemented at four centers of an HMO and an in-house pharmacy will be set up at two of these centers. The impact of each of these intervention strategies on the quality and ecomony of prescribing practices will be evaluated. Prescriptions and patient medical records will be reviewed for the six-month period prior to implementation of the formulary to assess the appropriateness of prescribing against criteria. Data on prescribing will also be collected after implementation of the formulary and the pharmacy and compared with the earlier data to determine any changes. In order to assess the effects of the formularly and the pharmacy on the economy of prescribing, both start-up and operational costs will be obtained. The project will also assess the acceptability of these two mechanisms to the prescribers at the HMO.